This invention relates generally to an improved tap wrench. More particularly, this invention relates to a tap wrench featuring a handle member and a tap-holding chuck, or collet, in an interlocking union that enables the handle member and chuck to be misaligned during the use of the tap wrench without negatively affecting a tapping operation.
When using prior hand-held tap wrenches to manually tap a hole, it is extremely important to maintain perfect axial alignment between the tap handle, tap chuck and tap comprising the tap wrench. Any axial misalignment between the afore-mentioned tap wrench components during the manual application of torque to most prior tap wrenches generally subjects the tap to undesirable stressful distorting forces, often culminating in tap breakage. Unfortunately, since taps are generally made of hard steel or similar materials, they are often relatively brittle, and little lateral pressure (i.e. force undesirably directed contrary to a primary axis of torque defined during tapping holes with a tap wrench) is required to accidentally break conventional taps. The elongated, relative slender design of taps also renders taps fragile and unsuitably resistant to the misalignment-induced lateral forces that are typically generated when prior rigid tap wrenches are employed in a less than ideal manner.
A general inability of users to apply torque to a tap wrench in an ideal manner is a major obstacle in the challenge of reducing tap breakage. This is largely due to the natural construction of the hand and wrist which creates a multi-positionable joint having such a wide range of movement that it is extremely difficult for one to maintain proper orientation between tap wrench, tap and work piece as the hand and wrist are used to provide the rotary twisting motion necessary for cutting internal threads in a work piece with a tap. Usually, only a very slight angularity of pressure on the tap wrench (i.e. pressure that is not directed along the longitudinal axis of the tap) will bind the tap in whatever work piece hole is being tapped and break the tap.
The avoidance of tap breakage, therefore, necessitates that one maintain the tap in an orientation which is perfectly perpendicular to the workpiece during the manual application of torque to the tap wrench. This alignment is very difficult to maintain, especially when the one tapping is in an awkward position or is tapping a workpiece situated in an inaccessible area. Moreover, optimum alignment between tap and work piece is also tough to achieve when tapping hard surface exotic metals or plastics, or when one is inexperienced in tapping holes.
A variety of past devices have been designed to address the problem of taps binding and breaking within the workpiece whenever misdirected applied force causes the tap to assume a non-perpendicular orientation relative to the surface of the workpiece.
Generally speaking such prior devices typically comprise a tap wrench handle member to which torque is manually applied, and another member of the wrench which provides the tap. These two tap wrench members are generally connected by a universal type joint which allows the handle member to be misaligned with the tap-holding member of the tap wrench without permitting the transference of misaligning forces from the handle member to the tap. However, past devices that incorporate a universal type joint to alleviate stress upon a tap are linked with several drawbacks.
A predominant form of universal type joint utilized in tools to permit axial misalignment between a driving member and a driven member (a functional feature highly desirable in tap wrenches) is a conventional ball and socket arrangement. However, utilization of a ball and socket joint in tap wrenches is less than ideal because manufacturing a ball and socket to allow smooth movement of the former within the latter disadvantageously requires the machining of close tolerances, thereby adding undesirably to the cost and/or complexity of the manufacturing process. In general, prior universal type joints typically used in tools have been expensive and difficult to manufacture and also have been difficult to disassemble and reassemble to replace worn parts. Moreover, some universal joints disadvantageously utilize a multi-yoke arrangement which doesn't allow a full range of movement for whatever elements are joined together.
Another criteria which has previously presented an obstacle to effective usage of a universal type joint in prior tap wrenches is the need for one tapping a hole to have a positive feel for the tapping resistance that the workpiece presents to the tap. That is, a tapping tool which incorporates a joint between tap handle and tap must ensure that the joint will not prevent one manipulating the handle from feeling the resistance encountered by the tap. Otherwise, the binding of the tap in the workpiece will be undetected until it is too late and the tap has broken. Thus, a tap wrench necessarily must be designed such that a user can sense tapping resistance. However, many prior tapping devices hinder the achievement of such sensitivity. For example, one prior type of jointed tapping tool is presented in U.S. Pat. No. 2,636,361, which utilizes a flexible joint comprising a ball of resilient material to join a handle member and a tapping member. However, the drawback associated with use of a resilient ball type joint in the context of a tap wrench is that the resilient material provides a shock deadening zone between tap and handle. This shock deadening zone makes it difficult for one manipulating the handle to accurately gauge, or get a sensitive feel for, the tapping resistance being encountered by the tap. As mentioned, this loss of sensitivity often results in broken taps. Yet another drawback associated with the use of a resilient material ball joint is that different applications of a jointed tapping tool will require a ball joint having a different Shore hardness. There exists, therefore, a significant need for an improved tap wrench designed such that misalignment forces exerted on a tap handle will not be transferred to the tap itself, thereby eliminating tap breakage and the resultant tap replacement costs and damage to the work piece. Additionally, an improved tap wrench is needed which translates tap resistance directly to the handle so that a user is provided with a positive feel of the tapping resistance and can operate the tap wrench accordingly. Such an improved tap wrench should incorporate a joint that allows misalignment of the tap and the handle (so that the improved tap wrench is usable in inaccessible places) and, ideally, such a joint should be provided without requiring the machining of close tolerances, as in a ball and socket joint or the use of shock-deadening materials which inhibit sensitivity to tap resistance. The present invention fulfills these needs in a rugged and relatively inexpensive fashion and provides further related advantages.